This is a complete online book (free to download) from MSDN that really goes into the real world problems of defining scope and the executing against requirements of a performance test. Although targeted at Web applications, the concepts are universal. If anyone gets asked to set do performance testing, then this is a great resource to define and set expectancies with your management team or sponsors.

This is a slide show of bullet points, but it makes a good self contained introduction to the subject of load testing. There are some good short notes on the definitions of functional testing, profiling (such as CPU and memory) and load testing. The overview also calls out the differences between load, stress and capacity testing. There is a six point load testing process on a single slide that lays out the basic steps of conducting a load test.